1. Field of the Invention
The present invention relates to a liquid crystal display device and, more particularly, to a liquid crystal display device capable of preventing a leakage of light to a corner area of the liquid crystal display device by altering the structure of a bottom cover, a guide panel, and an top cover.
2. Description of the Related Art
Recently, as diverse mobile electronic devices such as mobile phone, PDA, notebook computer, and the like, are advanced, demand for a flat panel display device which is lighter, thinner, shorter, and smaller that can be applicable to the devices is increasing. Research on a liquid crystal display (LCD), a plasma display panel (PDP), a field emission display (FED), a vacuum fluorescent display (VFD) has been actively conducted as a flat panel display device, and thanks to its advantages of being mass-produced, easiness of a driving unit, implementation of a high picture quality, realization of a large-scale screen, the LCD receives much attention.
The LCD is a transmissive display device that displays a desired image on a screen by adjusting the amount of light transmitting through a liquid crystal layer according to a refractive index anisotropy of liquid crystal molecules. Thus, the LCD includes a backlight, a light source, providing light that transmits through a liquid crystal layer to display an image. In general, the backlight is divided into two types: a side type backlight in which lamps are installed at the side of a liquid crystal panel and provide light to the liquid crystal layer; and a direct type backlight in which lamps provide light directly from a lower portion of a liquid crystal panel.
The side type backlight is installed at the side of the liquid crystal panel to provide light to the liquid crystal layer via a reflective plate and a light guide plate. Thus, because the side type backlight can contribute to reduce the thickness, it is largely used for a notebook computer, and the like, that requires a thin display device. However, the lamps for emitting light of the side type backlight are positioned at the side of the liquid crystal panel, the side type backlight cannot be applicable to a large liquid crystal panel and, in addition, because light is supplied through the light guide plate, a high luminance cannot be obtained. Thus, the side type backlight is not suitable for a liquid crystal panel in use for a large-scale LCD TV which recently draws much attention.
As for the direct type backlight, because light emitted from lamps is directly supplied to the liquid crystal layer, the direct type backlight can be applicable to a large liquid crystal panel. In addition, the direct type backlight has a high luminance, it can be largely used in fabricating a liquid crystal panel for an LCD TV.
Meanwhile, recently, a light emitting device which emits light by itself is used as a light source as a lamp of the backlight, instead of a fluorescent lamp. The light emitting device emits R, G, and B monochromatic light, so when it is applied for the backlight, it has a good color reproductivity and reduces driving power.
FIG. 1 is a schematic sectional view showing the structure of the related art LCD including a backlight having the LEDs as described above.
As shown in FIG. 1, the LCD includes a liquid crystal panel 10 including a first substrate 1, a second substrate 2, and a liquid crystal layer (not shown) interposed between the first and second substrates and implementing an image upon receiving a signal applied from an external source, an LED substrate 32 disposed at the side of a lower portion of the liquid crystal panel 10 and including a plurality of LEDs 34 emitting light, a light guide plate 35 disposed at the lower portion of the liquid crystal panel 10 and guide light emitted from the LEDs 34 to supply it to the liquid crystal panel 10, an optical sheet 38 provided between the liquid crystal panel 10 and the light guide plate 35 and including a diffusion sheet 38a for diffusing and concentrating light guided by the light guide plate 35 so as to be supplied to the liquid crystal panel 10 and prism sheets 38b and 38c, a reflective plate 36 disposed under the light guide plate 35 and reflecting light guide to the lower side of the light guide plate 35, a bottom cover 40 accommodating the reflective plate 36, the light guide plate 35, the optical sheet 38, and the LED substrate 32, a guide panel 42 coupled with the bottom cover 40 to assemble the reflective plate 36, the light guide plate 35, the optical sheet 38, and the LED substrate 32, on which the liquid crystal panel 10 being positioned, and an top cover 46 coupled with the guide panel 42 to assemble the liquid crystal panel 10.
The first substrate 1 of the liquid crystal panel 10 is a thin film transistor (TFT) array substrate including TFT. Various wirings and pixel electrodes, as well as the TFTs, are formed on the first substrate 1. The second substrate 2 is a color filter substrate, on which color filter layers and black matrixes are formed.
The backlight including the reflective layer 36, the light guide plate 35, the optical sheet 38, the LED 34, and the like is assembled to the bottom cover 40. A wall surface of the bottom cover 40 extends in an upward direction from a bottom surface, and the components of the backlight are placed at the interior of the wall surface to assemble the backlight. The top cover 46 is assembled with the guide panel 42 and the bottom cover 40 to assemble the liquid crystal panel 10 and the backlight.
However, the LCD device having such a configuration as described above has the following problem. That is, generally, when the LED 34 is used as a light source of the backlight, the bottom cover 40, the guide panel 42, and the top cover 46 are made of a metal having good thermal conductivity in order to effectively externally discharge heat generated from the LED 34 to prevent a rise in temperature of the backlight. In this case, when the bottom cover 40, the guide panel 42, and the top cover 46 are made of metal, they are pressed.
Meanwhile, the side extending in an upward direction or in a downward direction is formed at the bottom cover 40, the guide panel 42 and the top cover 46. Thus, the bottom cover 40, the guide panel 42, and the top cover 46 are formed through pressing, and in this case, in order to form the side extending in the upward direction or the downward direction by folding an outer area, the corners of the region where four sides are to be formed must be chamfered so as to be discontinuous.
Accordingly, because the four sides of the bottom cover 40, the guide panel 42, and the top cover 46 are formed to be discontinuous with the adjacent sides, separated by a certain interval, when the LCD device is assembled, light is leaked to the separated spaced. This will now be described with reference to FIG. 2.
FIG. 2 illustrates the relationships among the bottom cover 40, the guide panel 42, and the top cover 46 when the bottom cover 40, the guide panel 42, and the top cover 46 are assembled.
As shown in FIG. 2, when the sides of the bottom cover 40, the guide panel 42, and the top cover 46 are folded in the upward direction or in the downward direction, each side is discontinuous with the adjacent sides, leaving a separated space at the corner regions of the bottom cover 40, the guide panel 42, and the top cover 46.
Meanwhile, the LED substrate 32 is disposed at one side of the bottom cover 40, and the light guide plate 35 guiding light emitted from the LED 34 to the liquid crystal panel 10 is disposed on the bottom cover 40. Thus, light propagated to the corner of the light guide plate 35 among light made incident to the light guide plate 35 after being emitted from the LED 34 is leaked to outside through the separated space of the corners of the bottom cover 40, the guide panel 42, and the top cover 46, and this light leakage is a major cause of degrading quality of the LCD device.